Hi,

We are using RW_INTERLEAVED access as described in write_loop method in /test/pcm.c and opening 'default' device. However to disable the underruns, the snd_pcm_sw_params_set_stop_threshold is set to 0x7fffffff which is greater than boundary value. Period size is 1024 and buffer size is 2048. We try to write period_size no of frames using snd_pcm_writei.

This setup runs fine for several hours. It was left runing overnight. After some 12 hours of play, gdb is attached to the process and continued inside gdb. At this point, the thread went into a tight loop taking >100% cpu and playing same sound over and over again abusing speakers. It did not recover for a long time.

Stack trace shows that 'snd_pcm_dmix_sync_area' in pcm_dmix.c is taking a very long time to return because the 'size' is a large unsinged interger and mix_areas is getting called with 'transfer' value of <=2048.

Below is the stack trace: (gdb) bt #0 0xb7c44463 in mix_areas_32_smp (size=1360, dst=0xb6855000, src=0x84a7510, sum=0xb6845000, dst_step=4, src_step=4, sum_step=4) at pcm_dmix_i386.h:261 #1 0xb7c44d2b in mix_areas (dmix=0x84a7110, src_areas=0x84a51d0, dst_areas=0x84a6f00, src_ofs=0, dst_ofs=7168, size=1024) at pcm_dmix.c:193 #2 0xb7c45422 in snd_pcm_dmix_sync_area (pcm=0x84a71e0) at pcm_dmix.c:371 #3 0xb7c46680 in snd_pcm_dmix_mmap_commit (pcm=0x84a71e0, offset=0, size=1024) at pcm_dmix.c:813 #4 0xb7c07033 in snd_pcm_mmap_commit (pcm=0x84a71e0, offset=0, frames=1024) at pcm.c:6501 #5 0xb7c1804e in snd_pcm_plugin_mmap_commit (pcm=0x84a6d18, offset=0, size=1024) at pcm_plugin.c:434 #6 0xb7c07033 in snd_pcm_mmap_commit (pcm=0x84a6d18, offset=0, frames=1024) at pcm.c:6501 #7 0xb7c17956 in snd_pcm_plugin_write_areas (pcm=0x84a5390, areas=0xb68362b0, offset=0, size=1024) at pcm_plugin.c:290 #8 0xb7c074bb in snd1_pcm_write_areas (pcm=0x84a5390, areas=0xb68362b0, offset=0, size=1024, func=0xb7c177fc <snd_pcm_plugin_write_areas>) at pcm.c:6667 #9 0xb7c17cd5 in snd_pcm_plugin_writei (pcm=0x84a5390, buffer=0x84ab518, size=1024) at pcm_plugin.c:361 #10 0xb7bff1a7 in _snd_pcm_writei (pcm=0x84a6b18, buffer=0x84ab518, size=1024) at pcm_local.h:516 #11 0xb7bff16c in snd_pcm_writei (pcm=0x84a6b18, buffer=0x84ab518, size=1024) at pcm.c:1258

(gdb) f 2 #2 0xb7c45422 in snd_pcm_dmix_sync_area (pcm=0x84a71e0) at pcm_dmix.c:371 371 pcm_dmix.c: No such file or directory. (gdb) info locals dmix = 0x84a7110 slave_hw_ptr = 234156032 slave_appl_ptr = 7168 slave_size = 1057171456 appl_ptr = 0 size = 1018295296 transfer = 1024 src_areas = 0x84a51d0 dst_areas = 0x84a6f00 (gdb) p *dmix $1 = {type = SND_PCM_TYPE_DMIX, ipc_key = 5678293, ipc_perm = 432, ipc_gid = 17, semid = 32768, shmid = 65536, shmptr = 0xb6859000, spcm = 0x84a7340, appl_ptr = 217121792, last_appl_ptr = 233882624, hw_ptr = 233875428, avail_max = 0, slave_appl_ptr = 234156032, slave_hw_ptr = 234147996, slave_period_size = 1024, slave_buffer_size = 8192, slave_boundary = 1073741824, sync_ptr = 0xb7c4557c <snd_pcm_dmix_sync_ptr>, state = SND_PCM_STATE_RUNNING, trigger_tstamp = {tv_sec = 1392384066, tv_nsec = 8308000}, server = 0, client = 0, comm_fd = 0, hw_fd = 4, timer_fd = { fd = 3, events = 41, revents = 0}, poll_fd = 3, tread = 1, timer_need_poll = 0, timer_event_suspend = 131072, timer_event_resume = 262144, server_fd = 0, server_pid = 0, timer = 0x8496b90, interleaved = 1, slowptr = 1, max_periods = 0, channels = 2, bindings = 0x0, u = {dmix = { shmid_sum = 98305, sum_buffer = 0xb6837000, mix_areas_16 = 0xb7c443a8 <mix_areas_16_smp_mmx>, mix_areas_32 = 0xb7c44415 <mix_areas_32_smp>, mix_areas_24 = 0xb7c4451b <mix_areas_24_smp_cmov>, mix_areas_u8 = 0, remix_areas_16 = 0xb7c44638 <remix_areas_16_smp_mmx>, remix_areas_32 = 0xb7c446a5 <remix_areas_32_smp>, remix_areas_24 = 0xb7c447ab <remix_areas_24_smp_cmov>, remix_areas_u8 = 0}, dsnoop = {<No data fields>}, dshare = {chn_mask = 13151478482154389505}}, server_free = 0} (gdb) p *pcm $2 = {dl_handle = 0x0, name = 0x84a6e48 "dmix:0", type = SND_PCM_TYPE_DMIX, stream = SND_PCM_STREAM_PLAYBACK, mode = 0, poll_fd_count = 1, poll_fd = 3, poll_events = 1, setup = -1, monotonic = 0, access = SND_PCM_ACCESS_MMAP_INTERLEAVED, format = SND_PCM_FORMAT_S32_LE, subformat = SND_PCM_SUBFORMAT_STD, channels = 2, rate = 44100, period_size = 1024, period_time = 23219, periods = {min = 0, max = 0, openmin = 0, openmax = 0, integer = 0, empty = 0}, tstamp_mode = SND_PCM_TSTAMP_NONE, period_step = 1, avail_min = 1024, period_event = 0, start_threshold = 1024, stop_threshold = 2147483647, silence_threshold = 0, silence_size = 0, boundary = 1073741824, info = 2151743747, msbits = 32, rate_num = 44100, rate_den = 1, hw_flags = 0, fifo_size = 0, buffer_size = 2048, buffer_time = {min = 0, max = 0, openmin = 0, openmax = 0, integer = 0, empty = 0}, sample_bits = 32, frame_bits = 64, appl = {master = 0x0, ptr = 0x84a7130, fd = -1, offset = 0, link_dst_count = 0, link_dst = 0x0, private_data = 0x0, changed = 0}, hw = { master = 0x0, ptr = 0x84a7138, fd = -1, offset = 0, link_dst_count = 0, link_dst = 0x0, private_data = 0x0, changed = 0}, min_align = 1, mmap_rw = 1, mmap_shadow = 0, donot_close = 0, mmap_channels = 0x84a54a0, running_areas = 0x84a51d0, stopped_areas = 0x0, ops = 0xb7c91860, fast_ops = 0xb7c918a0, op_arg = 0x84a71e0, fast_op_arg = 0x84a71e0, private_data = 0x84a7110, async_handlers = {next = 0x84a72e4, prev = 0x84a72e4}}

Attaching gdb does not show this behaviour if snd_pcm_sw_params_set_stop_threshold is not set, which then defaults to buffer size or when the application is running for shorter duration.

Is it that setting of stop threshold to 0x7fffffff is triggering this and attaching gdb is making the buffer pointers misbehave? If so, what can be done if we do not want PCM to stop.

Below is the pcm dump: Plug PCM: Linear conversion PCM (S32_LE) Its setup is: stream : PLAYBACK access : RW_INTERLEAVED format : S16_LE subformat : STD channels : 2 rate : 44100 exact rate : 44100 (44100/1) msbits : 16 buffer_size : 2048 period_size : 1024 period_time : 23219 tstamp_mode : NONE period_step : 1 avail_min : 1024 period_event : 0 start_threshold : 1024 stop_threshold : 2147483647 silence_threshold: 0 silence_size : 0 boundary : 1073741824 Slave: Soft volume PCM Control: PCM Playback Volume min_dB: -51 max_dB: 0 resolution: 256 Its setup is: stream : PLAYBACK access : MMAP_INTERLEAVED format : S32_LE subformat : STD channels : 2 rate : 44100 exact rate : 44100 (44100/1) msbits : 32 buffer_size : 2048 period_size : 1024 period_time : 23219 tstamp_mode : NONE period_step : 1 avail_min : 1024 period_event : 0 start_threshold : 1024 stop_threshold : 2147483647 silence_threshold: 0 silence_size : 0 boundary : 1073741824 Slave: Direct Stream Mixing PCM Its setup is: stream : PLAYBACK access : MMAP_INTERLEAVED format : S32_LE subformat : STD channels : 2 rate : 44100 exact rate : 44100 (44100/1) msbits : 32 buffer_size : 2048 period_size : 1024 period_time : 23219 tstamp_mode : NONE period_step : 1 avail_min : 1024 period_event : 0 start_threshold : 1024 stop_threshold : 2147483647 silence_threshold: 0 silence_size : 0 boundary : 1073741824 Hardware PCM card 0 'HDA Intel PCH' device 0 subdevice 0 Its setup is: stream : PLAYBACK access : MMAP_INTERLEAVED format : S32_LE subformat : STD channels : 2 rate : 44100 exact rate : 44100 (44100/1) msbits : 32 buffer_size : 8192 period_size : 1024 period_time : 23219 tstamp_mode : ENABLE period_step : 1 avail_min : 1024 period_event : 0 start_threshold : 1 stop_threshold : 1073741824 silence_threshold: 0 silence_size : 1073741824 boundary : 1073741824 appl_ptr : 0 hw_ptr : 0

Thanks